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Author
Topic: Changing time of day for labs? (Read 2528 times)

I have always had labs done in the early evening, but for the next set my doctor wants me to have "fasting labs" (for reasons unrelated to HIV). I cannot come in in the morning as I start work very early, so I've scheduled an appointment for the earliest time possible--around 1:30, I think, in the afternoon. That still means not eating anything since dinner the night before but I suppose skipping breakfast for one day isn't a big deal. ( I can drink water, can't I?)

Here's the question: I've just noticed on thebody.com someone saying that it is important to get our blood drawn at the same hour every time because our T-cells naturally fluctuate throughout the day, descending from a moderate number in the morning to a low point in the afternoon and then climbing again to a high number in the evening. One man who was in a study always got his blood drawn, for the study, in the morning, but for his own doctor, in the evening, and the first tests were always around 500 but the latter around 800. So, if my next set of labs are done at 1:30, will that give me a lower t-cell count than if I waited until the evening? Also, would fasting depress T-cell count? Should I reschedule this appointment?

I have fasting labs around once per year for cholesterol. I always prefer to have my labs and all other appointments in the afternoon because of having to be certain it is safe to leave the bathroom bowl every day. I call it the 3 minute warning and I can usually leave the house by noon.

For fasting labs, you can have water and nothing else. The part about your T Cells being higher a certain time of day is not something I have heard but I have heard labs taken twice in the same day can vary by 50. Only 1 time in 14 years of labs have I gone for my follow up with doctor and gotten labs again. Have the best dayMichael

Since most labs aren't taken at 830pm, most people never get their highest counts taken anyway. I would venture to say that a large amount of positive people have their counts taken mid-to-late morning meaning they are always actually getting their lowest counts

Of course, tcell counts fluctuate throughout the day, and are affected by diet, exercise (the count is much lowered for up to an hour after exercising before rebounding to a high count), stress, etc. So there really no single number, but a range for any given day.

Daily variation of CD4 counts

Only one study concerning the daily, or diurnal, variation in CD4 counts will be reviewed here (Malone et al. 1990). The authors compared the diurnal variation in HIV-positive and HIV-negative people, finding a significant variance in both. They found that greater variations occurred in HIV-negative people, but that both groups followed a pattern that coincides with known daily fluctuations of cortisol, with minimum CD4 levels occuring between 8:00 and 10:00 a.m., and maximums occuring at around 10:00 p.m.... People with lower baseline CD4 counts had much less diurnal variation. This pattern is often seen in people under chronic stress where the normal variation of cortisol secretion is severely flattened. HIV-negative people had an average variation of 506 cells/mm3 each day, while HIV-positive people had only about 60 cells/mm3 of variation. http://www.healtoronto.com/irwincd4.html

so there are a couple of things to consider:1) the difference in very slight2) how much do you care? if you've remained undetectable and you have a difference of only 60 tcells, is that data (a slightly lowered count) really going to impact your treatment? Considering your tcells counts are actually in a range everyday, you'll probably never have exactly the same tcell count anyway even if you have the lab work done at the same time of day each time.

I was told to just fast for 12 hours when I got my cholesterol/trys screened. Actually, another doc said 8. I think 12 is still considered best. So, why couldn't you eat something right before bed? I've actually heard some say to get our real results we should not fast at all. They were saying fasting doesn't give a real picture of what our cholesterol is throughout the day. That is a discussion for another day I suppose and I don't know if he knew what he was talking about.

About CD4, I always get my bloodwork done around 2-3pm. What you said got me to thinking. If someone had a difference from 800 to 500 depending on what time of day, that would totally affect treatment guidelines and HAART initiation. However, I suppose the CD4% would be the same?? Or, would that be different too? My lab closes at 4pm, so I couldn't get it any later.

If someone had a difference from 800 to 500 depending on what time of day, that would totally affect treatment guidelines and HAART initiation. However, I suppose the CD4% would be the same?? Or, would that be different too?

http://www.healtoronto.com/irwincd4.htmlThe authors caution that even this blunted variation is significant, however, stating "3 of 12 HIV-positive patients had CD4+ cell counts below 200 cells/mm3 in the morning but had greater than 200 cells/mm3 in the afternoon" (Malone et al. 1990, page 150). In other words, in the morning they would be diagnosed with AIDS, but if their blood was checked in the afternoon they would just be HIV-positive, albeit with a relatively low T-cell count. They found similar results for total lymphocyte counts, but CD4/CD8 ratios did not have statistically significant changes.(just goes to show that the label "AIDS" is just a label )

ah but if you're trying to go in late to get that higher number, then you're not really getting a "true" number of what you actually had throughout the day, just like the fasting alters the cholestrol number. Plus once again, it's not one tcell count number for the day; but a range. What would be the reason to always go in late to get the higher number? To artifically inflate the cd4 count on paper, so it seems like you have more? To trick yourself into "feeling better" because you think you have more? Then again, according to that research that was mentioned in my link, HIV+ people have less of a diurnial variation, so going at a certain time to get a higher count probably doesn't really give that number much of a boost anyway.

up until recently I was on videx ec which has to be taken 2hr before or after food. since I haven't eaten breakfast since my college days, I always just took this med first thing in the am. For those "fasting" tests, I just scheduled them before lunch, so I usually went 8-10 hours of that fasting time by being asleep.

After the test, which was done at the hospital lab, I always stopped in to the McD's (located in the hospital's connected medical office blding) to get some nice artery-clogging burger and fries.

The CD4 cell value can change a lot. Time of day, fatigue, and stress can affect the test results. It's best to have blood drawn at the same time of day for each CD4 cell test, and to use the same laboratlory.

And this is someone at Johns Hopkins:

To minimize variation, get them drawn at roughly the same time of day and use the same lab each time.

Leatherman, you ask good questions: how important is it? How much should I care? The answer is probably (since it will be just one test in a long series) not much. But the point is not to get blood drawn as late as possible in order to cheer oneself up by getting the best numbers possible, but rather to get them done at about the same hour every time so that the list of numbers says something meaningful about trends over time.

The studies you cite mention a difference of 60 t-cells, which is indeed slight. But the exchange at the thebody.com (which for the life of me I cannot find again, goodle away though I try) said something like this: the guy was regularly getting t-cell counts of around 800, in the evening, but then for the study he was in he was getting them done in the morning, and they were around 500. And the person leading the study starting pressuring him to start HAART because he had lost 300 t-cells since the last test--he was "progressing", and he had to research diurnal variations and insist that it was insignificant.

So, if I went in at the usual hour next time and they told me I had 300 t-cells, that would be a meaningful event. I obviously wouldn't rush to start treatment based on one single test, but I would feel that my experience with HIV had entered on a new phase. I would certainly await the next set of labs with a great deal of anxiety. But if, on the other hand, I went in at 1:30 and it came back with 300 t-cells I would end up saying "It's just diurnal variation", put a mental asterisk next to that set of labs, and more or less ignore them. The whole episode would create some confusion and anxiety, but it would not be a meaningful contribution to the picture of trends over time.

Secondly, both the study you cite and thebody.com mention "diet" as a contributing factor to variation in t-cell count. What effect on t-cells would be exerted by one's not having eaten anything for twelve (or eight) hours?

As silly as it sounds, there is an element of psychology in the whole thing. You appropriately point out the meaninglessness of an "AIDS" diagnosis by pointing out that even with the slight, 60 t-cell variation, someone who gets tested in the morning will get an AIDS diagnosis who might not have done so had he waited until evening. That might well be psychologically significant for some people. (Or, if someone was hoping for public assistence, he might deliberately get tested in the morning!)

TednLou,

If your lab closes at four, what do people do who work full time and don't finish until five or six, which was my case until recently?

As for eating right before bed, I'm not sure whether that would mitigate the hunger of the next afternoon much--sometimes I'm hungrier the next morning when I eat right before bed! But as I said, I guess I'll survive one day without breakfast.

While we're on these subjects, it is interesting to note that there can also be variation according to which laboratory does the test. Why? Do different labs have different procedures? How great is the difference?

Finally, since I'm sure I'm not the only one to get fasting labs, has anyone else here had a significantly "different" t-cell count on a fasting day? Or on a day when you got your labs done much earlier than usual?

If your lab closes at four, what do people do who work full time and don't finish until five or six, which was my case until recently?

As for eating right before bed, I'm not sure whether that would mitigate the hunger of the next afternoon much--sometimes I'm hungrier the next morning when I eat right before bed! But as I said, I guess I'll survive one day without breakfast.

While we're on these subjects, it is interesting to note that there can also be variation according to which laboratory does the test. Why? Do different labs have different procedures? How great is the difference?

Finally, since I'm sure I'm not the only one to get fasting labs, has anyone else here had a significantly "different" t-cell count on a fasting day? Or on a day when you got your labs done much earlier than usual?

That is a good question about people who work late. I'm not sure. I go to the university's HIV clinic and use their lab. I guess people who go to other docs probably go to LabCorp. I think many of us prefer the HIV clinic believing they are more experienced. I suppose people have to do it on their lunch breaks or maybe take time off. That is a good question.

When I fasted, I wondered whether not eating for so long would affect my t-cells, too. However, they actually went up. As for different labs, I've often wondered if I had my bloodwork done at another lab, every time, what my numbers would show. I suppose they should be somewhere near what they are now. It still makes me wonder if I'd have a much lower or higher result. It is just those things that make ya wonder but I suppose don't mean much and probably wouldn't be much different.

Good luck on everything. I know my dad hates having to fast for tests. He gets low sugar or something if he doesn't eat every few hours. I've noticed sometimes I can go forever without eating and other days I become a real bitch without food.

So, if I went in at the usual hour next time and they told me I had 300 t-cells, that would be a meaningful event. I obviously wouldn't rush to start treatment based on one single test, but I would feel that my experience with HIV had entered on a new phase.

You leave out a very important issue though when discussing this - Viral Load.

If you are not on meds and got that 300 count (after having say regularly close to 500) but still with a VL of only 10k - would that be a meaningful event? Not really. However, if the tcells dropped and the VL took a serious increase, then you might have an event.

On the other hand, if you're on meds, undetectable, and have a cd4 change from 500 to 300 in only one test, that would not be a meaningful event in itself either. It could be a lab error, you were stressed, hungry, tired, just exercised, etc. or even just the "wrong" time of day. You would definitely have to wait until the next test to know.

but rather to get them done at about the same hour every time so that the list of numbers says something meaningful about trends over time.

OR do like I do. Some tests are in the morning and some are in the afternoon (there have been a lot of these tests over nearly 20 yrs) and let the natural normal randomness of the hourly/daily tcell flucuation be factored in.

The reason I'm nonchalant and downplaying this issue is because you cannot get too worried about one set of numbers. Why? I've already been doing this for nearly 20 yrs, with hopefully another 20 yrs to go. If I freaked out about every VL blip or every inconsistent cd4 result, well I would have already gone crazy by now. LOL (no comments from the pnut gallery please. LOL)

as to laboratory variatonshttp://gateway.nlm.nih.gov/MeetingAbstracts/ma?f=102208349.htmlThus laboratory factors accounted for 15% of the variation between visits. Variation in the absolute WBC, lymphocyte % and CD4% accounted for 52%, 29% and 19% of the physiologic variation in CD4 counts respectively. CONCLUSIONS: Our results confirm a high degree of variability of CD4 counts among HIV infected individuals, largely attributable to physiological factors. This variability can be minimized more effectively by repeating CD4 counts over time than by repeating measurements at a single visit. Our data further suggest that the variability of CD4 counts can be reduced by 80%, and at lower cost, if a single CD4 fraction is utilized with the lymphocyte count repeated over time.

While we're on these subjects, it is interesting to note that there can also be variation according to which laboratory does the test. Why? Do different labs have different procedures? How great is the difference?

I'm not certain of the "whys" but different labs can return difference results, and can use a different test to determine the results. One lab that processed my tests in OH returned <75 as UD while the other lab returned <50 as UD. I believe the lab here in SC returns <50 as UD. I've never cared enough about some miniscule changes to look into the reasons behind the difference in cd4 testing and lab variations (though lab variations have been known to happen with nearly all numbers from ANY test)